advice regarding softie's future

i'd like your opinions on what i should do with my softie. i've had him in my dorm room since september, but now he's a good 12cm long. i'm saving for a twenty gallon tank as of this moment, and will be keeping him at home during the summer. but the problem is next school term. i really don't think i can keep up with caring for a 20 gallon tank next year in a small single dorm room. i love my turtle, and i want to make sure he gets the care and attention that i give him every day. i can't leave him at home with my parents, and i don't know anyone to whom i could give him. what should i do?